Non-generic concentrations in shape-memory alloys; the case of CuZnAl
It is well known that a solid-to-solid, symmetry-breaking, martensitic phase transition is at the basis of the remarkable properties of many 'active' crystalline materials (for instance, shape-memory alloys). Aided by the detailed kinematical analysis of the phase transitions and of the related twins that can occur in simple lattices, we have recently given some explicit conditions that can improve the twinning ability and hence the macroscopic behavior of a class of shape-memory alloys, i. e. those undergoing a cubic-to-monoclinic transformation. We discuss some explicit theoretical guidelines for determining the special concentrations which may allow for the formation of extra twins in suitable alloys, and thus enhance their memory features. We propose to test such thoretical predictions, by studying experimentally the crystallographic structure, transformation twins, and mechanical behavior of suitable CuZnAl alloys. This approach shows how the theoretical investigation of phase transitions and related phenomena can assist in the search or design of new materials with improved performance.